The present invention generally concerns a locking device for a fluid plug-in connection between one end of a fluid pipe and a connecting part, and more particularly to an arrangement for preventing insertion of the locking device unless the parts of the fluid plug-in connection are properly positioned.
A locking device of the general type concerned here for a quick action coupling is disclosed by German Published, Unexamined Patent Application (DE-OS) 3,440,753. This quick action coupling contains a coupling nipple which has to be screwed by an internal thread onto the end of the fluid pipe to be connected. The coupling nipple can then be inserted into a coupling sleeve, which represents the connecting part, up to a stop and can be secured in the connecting part by a U-shaped sealing piece which can be inserted into a guide slot or recess of the coupling sleeve, two branches of the sealing piece overlapping a radially protruding abutment of the coupling nipple.
Also disclosed is a substantially simpler, and therefore more cheaply manufacturable plug-in connection for pipes, particularly in motor vehicles, having a U-shaped lockings clamp guided in guide holes as shown in German Published, Unexamined Patent Application (DE-OS) 1,425,470. It can be used in hydraulic systems of vehicles wherever individual fluid pipes have to be connected by plugging into connecting parts of valves, lifting cylinders and the like. The high pressures occurring, up to 190 bar, demand positive pipework locking. The design arrangement of this locking system and plug-in connection greatly aids the simplification of the manufacture, assembly and maintenance because the fluid pipe itself is provided with an upset, radially protruding, circumferential abutment in collar shape, which is overlapped by a U-shaped clamp guided transversely to the axis of the connecting hole in two guide holes tangentially penetrating the connecting hole of the connecting part. No special plug is required for this type of plug-in connections so that sealing problems between a plug and the fluid pipe which has to be connected are avoided ab initio.
However, it is not possible to exclude erroneous, i.e. incorrectly or incompletely plugged-in connections, by means of the two above-noted locking devices, because the plane of the guide holes for the clamp must necessarily be located at a distance below the plug-in side of the connecting part. It can therefore occur that the clamp, or its two branches, are inserted under the abutment of a fluid pipe, which is not correctly plugged in, instead of correctly overlapping the abutment. However, because the abutment can, even then, be immersed in the connecting hole, the connection appears to be correctly plugged in and locked, from a superficial visual inspection.
Other locking devices for fluid plug-in connections which have a U-shaped locking clamp are also disclosed. Thus, for example, such a locking device is known from German Published, Examined Patent Application (DE-AS) 2,542,284 which, however, does not secure individual fluid pipes but, rather, plug-in elements which combine several fluid pipes into blocks the clamp being guided in guide holes, as in the state of the art forming the generic type of plug-in connection already discussed.
A locking device with a U-shaped clamp for fluid plug-in connections is also disclosed by German Published, Unexamined Patent Application (DE-OS) 2,849,133 in which individual plugs, each tightly connected to a fluid pipe, can be locked in connecting holes. In this case, furthermore, the guide of the clamp is open towards the plug-in side of the connecting part but, in contrast to the presently disclosed locking device, not along the length of but transversely to the insertion direction of the clamp. Although visual inspection of the plug-in connections produced by widening of the already fully inserted clamps is also possible in this case, it does not lead to such unambiguous results as those of the locking device of the present application because of the shape of the plug.
Also, a U-shaped clamp is known from DE-GM 7,918,697 for joining together two fluid pipes aligned axially or for joining a fluid pipe and a connecting part accepting it, which clamp overlaps on the outside an abutment formed by peripheral grooves on each of the two fluid pipes or on one fluid pipe and the connecting part.
Therefore, an object of the present invention is to provide improved assembly reliability of a locking device for a plug-in connection between a fluid pipe and a connection part.
These and other objects are achieved in certain preferred embodiments of the present invention by employing an arrangement which prevents insertion of the plug-in connection unless all parts of the connection are properly positioned.
Thus, in certain preferred embodiments of the present invention, the guide slot for the locking clamp is open to the plug-in side of the connecting part by a longitudinal opening. The clamp itself is provided with a guard which extends at least over the total depth within the elongated opening. When the clamp is inserted into the guide slot, the guard extends over a defined space within the elongated opening which reduces the clearance of the elongated opening, projected in the insertion direction, to a dimension which is smaller than the external dimension of the abutment on the fluid pipe.
This description, which applies more to the mode of operation, makes it clear that the problem described above, i.e. that the clamp runs under the abutment of the fluid pipe instead of overlapping it, can no longer occur in the manner stated if the locking device and guard arrangement is used according to preferred embodiments of the present invention. This is because the guard at least ensures that, when the clamp is inserted, the abutment is either seated properly in the connecting hole, where it belongs, or remains easily visible above the plug-in side of the connecting part. In intermediate positions of the abutment, the clamp simply cannot be inserted because the guard then runs into the abutment.
No disclosure of the arrangement of the present application with respect to either the guidance of the clamp or the clamp itself, can be obtained from any of the items mentioned above. In particular, a guard formed on the clamp and inevitably colliding with an abutment incorrectly positioned in the connecting hole cannot be deduced from the disclosure of the items discussed above.
According to certain preferred embodiments of the present invention, there are several possibilities for the geometric configuration of the guide slot elongated opening satisfying the specified requirements, e.g. T-groove guidance or dovetail type guides. In addition, different configurations of the clamp itself are disclosed; among these, one form with a preassembly capability is particularly emphasized.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.